The mouse core is devoted to production of non-commercially available murine lines and maintenance of all mice used in conjunction with this program project. This includes all purchased animals, mice bred specifically for use in this program, and all maintenance of all experimental animals. The operation of such a core is justified by the significant overlap among investigators in the transgenic lines used in each project and by the fact that many experiments will be performed as collaborative efforts. It is anticipated that there will be equal use of the animal core by each investigator.